Image encoder, image encoding method, recording medium and computer data signal embodied in a carrier wave

ABSTRACT

A processor performs layout analysis, and classifies pieces of bitmap data into a character area and a picture area. The processor divides each of the character area and the picture area into a plurality of tiles having a predetermined shape, thereby creating a table including information representing either character attribute or picture attribute in association with each tile number. The processor performs scalar quantization for data of each tile using a quantization coefficient for characters or pictures, based on the created table. The processor encodes the data of each tile using an SNR progressive technique or a resolution progressive technique, and performs post quantization for the data using a quantization parameter for characters or pictures. Then, the processor stores the encoded data into a storage device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image encoder, an image encodingmethod, a recording medium and a computer data signal embodied in acarrier wave, for encoding electronic documents in consideration of thehuman recognition characteristics, thereby processing the electronicdocuments to be easily recognized by users and to be rapidly displayed.

2. Description of the Related Art

Recently, for the sake of conservation of natural resources or for thesake of cost reduction in office, paperless processing using IT(Information Technology) is becoming popular in companies, etc. As onepaperless method, there is a technique for transforming paper documentsinto electronic documents. An image encoder (information encoder) readsout and digitizes information of characters or figures printed on apaper document by using a scanner, and stores the read and digitizedinformation in an internal hard disk, etc. A user specifies anelectronic document stored in the image encoder and displays thespecified document on a display, so that the user can view the sameinformation as that printed on the paper document.

The image encoder generally includes a search function for searching fora predetermined electronic document from a mass of electronic documentsstored therein. To effectively use the search function, a keyword forsearch is attached to the electronic document. Upon reception of asearch instruction together with the keyword input through the keyboard,etc., the image encoder begins searching a target electronic document.

To enhance the storage performance or transmission performance of theelectronic documents, the image encoder reduces the amount of data to beencoded when transforming the paper documents into electronic documents.

The image encoder may transmit and display an electronic document usinga progressive technique. According to a progressive technique, alow-quality image, whose resolution, gradation and frequency bandwidthare not initially in a sufficient level, is transmitted and displayed.Subsequently, additional information is transmitted piece by piece togradually improve the quality of the image, and then the image with thebest quality can be transmitted and displayed.

If an electronic document is transmitted using a progressive technique,a terminal which is connected to the image encoder displays apoor-quality image, and displays the image which will gradually beimproved in its quality. In the end, the terminal can displays thebest-quality image.

However, as compared to paper documents, the above-described imageencoder (electronic documents) can not easily be handled by the users.Hence, the image encoder can not widely be spread, so that the paperlessprocessing can not widely and efficiently be performed.

In the case where the electronic document is stored in the imageencoder, the user needs to affix a reference keyword (for search) to thedocument. The user may feel trouble to set a certain keyword, or mayhave some difficulty with it. In the case where an unsuitable keyword isattached to the electronic document, this document can not be searchedout. For example, if a keyword of “good-looking cloth” which is a user'ssubjective and personal expression is attached to a predeterminedelectronic document, this electronic document can not searched out basedon any of ordinary keywords.

Usually, when people have the newspaper or magazine in their hand, theydo not read only a target article in the newspaper or magazines. First,people briefly read the newspaper, find out an interesting article inthe newspaper or magazines, and read the detail of the articleafterwards.

This reading manner can not be accepted for the image encoder. In theimage likewise the case of paper documents. However, according toconventional image encoders, transmission or displaying of data requiresa long period of time, so that users can not just freely read the pluraldocument pages.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the above. It isaccordingly an object of the present invention to provide an imageencoder, an image encoding method, a recording medium and a computerdata signal embodied in a carrier wave, for overcoming theabove-described conventional technique, and for encoding an electronicdocument in accordance with human recognition characteristics, so thatusers can easily recognize a target electronic document and that thedocument can rapidly be displayed.

In order to achieve the above object, according to the first aspect ofthe present invention, there is provided an image encoder comprising:

an analyzer which analyzes image data, and classifies a plurality ofunit areas of the image data into a plurality of attributes;

an encoder which encodes image data of each of the plurality of unitareas using a corresponding one of a plurality of progressivetechniques, in accordance with a corresponding attribute classified bythe analyzer; and

a storage section which stores the image data encoded by the encoder inunit of each unit area.

According to this invention, the analyzer analyzes the image data (e.g.bitmap data), and classifies data of each of a plurality of unit areas(tiles) into any of a plurality of attributes (e.g. a characterattribute and a picture attribute). The encoder encodes data of each ofthe plurality of unit areas using a corresponding one of a plurality ofprogressive techniques (e.g. an SNR progressive technique and aresolution progressive technique), in accordance with the classifiedattribute. The storage section stores the image data which is encoded bythe encoder in the unit of unit areas. Thus encoded image data isdecoded using a corresponding progressive technique, based on theattribute of each unit area. For example, in the case where theattribute of a corresponding one of the plurality of unit areas is thecharacter attribute, the data of the corresponding unit area is decodedusing the SNR progressive technique. On the contrary, in the case whereattribute is the picture attribute, the data of the corresponding unitarea is decoded using a resolution progressive technique. Hence, in theimage to be displayed on a predetermined display device, characters canbe recognized by the user, before the data is completely decoded usingthe SNR progressive technique. On the other hand, pictures in the imagecan be recognized by the user, before the data is completely decodedusing the resolution progressive technique. In this manner, anelectronic document is encoded in consideration of the human recognitioncharacteristics, so that users can easily recognize a target electronicdocument and that the document can rapidly be displayed.

In order to achieve the above object, according to the second aspect ofthe present invention, there is provided an image encoder comprising:

an analyzer which analyzes image data including at least one characterarea and one picture area, and classifies a plurality of unit areas intoa character attribute indicating that the image data is in the characterarea or a picture attribute indicating that the image data is in thepicture area;

an encoder which encodes image data of each of the plurality of unitareas using a corresponding one of two progressive techniques, inaccordance with whether the analyzer classifies the image data into thecharacter attribute or the picture attribute; and

a storage section which stores the image data encoded by the encoder.

According to this invention, the analyzer analyzes image data (e.g.bitmap data) including at least one character area and one picture area,and classifies a plurality of unit areas (tiles) into a characterattribute indicating that the image data is in the character area or apicture attribute indicating that the image data is in the picture area.The encoder encodes image data of each of the plurality of unit areasusing a corresponding one of two progressive techniques (e.g. the SNRprogressive technique and the resolution progressive technique), inaccordance with whether the analyzer classifies the image data into thecharacter attribute or the picture attribute. The storage section storesthe image data encoded by the encoder. Thus encoded image data isdecoded using a corresponding progressive technique, based on theattribute of each unit area. For example, in the case where theattribute of a corresponding one of the plurality of unit areas is thecharacter attribute, the data of the corresponding unit area is decodedusing the SNR progressive technique. On the contrary, in the case whereattribute is the picture attribute, the data of the corresponding unitarea is decoded using a resolution progressive technique. Hence, in theimage to be displayed on a predetermined display device, characters canbe recognized by the user, before the data is completely decoded usingthe SNR progressive technique. On the other hand, pictures in the imagecan be recognized by the user, before the data is completely decodedusing the resolution progressive technique. In this manner, anelectronic document is encoded in consideration of the human recognitioncharacteristics, so that users can easily recognize a target electronicdocument and that the document can rapidly be displayed.

The encoder may:

encode, in a case where the analyzer classifies a corresponding one ofthe plurality of unit areas into the character attribute, image data ofthe corresponding one of the plurality of unit areas using an SNRprogressive technique; and

encode, in a case where the analyzer classifies the corresponding one ofthe plurality of unit areas into the picture attribute, image data ofthe corresponding one of the plurality of unit areas using a resolutionprogressive technique.

In order to achieve the above object, according to the third aspect ofthe present invention, there is provided an image encoder comprising:

an analyzer which analyzes image data including at least one characterarea and at least one picture area, and classifies a plurality of unitareas into a character attribute indicating that the image data is inthe character area or a picture attribute indicating that the image datais in the picture area;

a scalar quantization section which performs scalar quantization forimage data of each of the plurality of unit areas using a correspondingone of two quantization coefficients, in accordance with whether theanalyzer classifies the image data into the character attribute or thepicture attribute;

an encoder which encodes the image data of each of the plurality of unitareas which is quantized by the scalar quantization section using acorresponding one of two progressive techniques, in accordance withwhether the analyzer classifies the image data into the characterattribute or the picture attribute;

a post quantization section which is performs post quantization for theimage data of each of the plurality of unit areas which is encoded bythe encoder using a corresponding one of two quantization parameters, inaccordance with whether the analyzer classifies the image data into thecharacter attribute or the picture attribute; and

a storage section which stores the image data of each of the pluralityof unit areas which is post quantized by the post quantization section.

According to this invention, an analyzer analyzes image data (e.g.bitmap data) including at least one character area and at least onepicture area, and classifies a plurality of unit areas (tiles) into acharacter attribute indicating that the image data is in the characterarea or a picture attribute indicating that the image data is in thepicture area. The scalar quantization section performs scalarquantization for image data of each of the plurality of unit areas usinga corresponding one of two quantization coefficients (e.g. quantizationcoefficients for characters and pictures), in accordance with whetherthe analyzer classifies the image data into the character attribute orthe picture attribute. The encoder which encodes the image data of eachof the plurality of unit areas which is quantized by the scalarquantization section using a corresponding one of two progressivetechniques, in accordance with whether the analyzer classifies the imagedata into the character attribute or the picture attribute. The postquantization section performs post quantization for the image data ofeach of the plurality of unit areas which is encoded by the encoderusing a corresponding one of two quantization parameters (e.g. aparameter for characters and a parameter for pictures), in accordancewith whether the analyzer classifies the image data into the characterattribute or the picture attribute. The storage section stores the imagedata of each of the plurality of unit areas which is post quantized bythe post quantization section. Thus encoded image data is decoded usinga corresponding progressive technique, based on the attribute of eachunit area. For example, in the case where the attribute of acorresponding one of the plurality of unit areas is the characterattribute, the data of the corresponding unit area is decoded using theSNR progressive technique. On the contrary, in the case where attributeis the picture attribute, the data of the corresponding unit area isdecoded using a resolution progressive technique. Hence, in the image tobe displayed on a predetermined display device, characters can berecognized by the user, before the data is completely decoded using theSNR progressive technique. On the other hand, pictures in the image canbe recognized by the user, before the data is completely decoded usingthe resolution progressive technique. In this manner, an electronicdocument is encoded in consideration of the human recognitioncharacteristics, so that users can easily recognize a target electronicdocument and that the document can rapidly be displayed.

The scalar quantization section may perform scalar quantization for theimage data of each of the plurality of unit areas using a predeterminedquantization coefficient for characters, in a case where the analyzerclassifies a corresponding one of the plurality of unit areas into thecharacter attribute, and perform scalar quantization for the image dataof each of the plurality of unit areas using a predeterminedquantization coefficient for pictures, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thepicture attribute;

the encoder may encode the image data of each of the plurality of unitareas using an SNR progressive technique, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thecharacter attribute, and encode the image data of each of the pluralityof unit areas using a resolution progressive technique, in a case wherethe analyzer classifies the corresponding one of the plurality of unitareas into the picture attribute; and

the post quantization section may perform post quantization for theimage data of each of the plurality of unit areas using a predeterminedquantization parameter for characters, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thecharacter attribute, and perform post quantization for the image data ofeach of the plurality of unit areas using a predetermined quantizationparameter for pictures, in a case where the analyzer classifies thecorresponding one of the plurality of unit areas into the pictureattribute.

The analyzer may analyze the image data including the at least onecharacter area and at least one picture area in accordance with whetherthe image data represents a high-contrast image or a low-contrast image,classify a corresponding one of the plurality of unit areas into anhigh-contrast attribute indicating that the image data represents thehigh-contrast image or a low-contrast attribute indicating that theimage data representing the low-contrast image;

the scalar quantization section may perform scalar quantization for theimage data of each of the plurality of unit areas using a predeterminedquantization coefficient for characters in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thehigh-contrast attribute, and perform scalar quantization for the imagedata of each of the plurality of unit areas using a predeterminedquantization coefficient for pictures, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thelow-contrast attribute;

the encoder may encode the image data of each of the plurality of unitareas using an SNR progressive technique, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thehigh-contrast attribute, and encode the image data of each of theplurality of unit areas using a resolution progressive technique, in acase where the analyzer classifies the corresponding one of theplurality of unit areas into the low-contrast attribute; and

the post quantization section may perform post quantization for theimage data of each of the plurality of unit areas using a predeterminedpost quantization parameter for characters, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thehigh-contrast attribute, and perform post quantization for the imagedata of each of the plurality of unit areas using a predetermined postquantization parameter for pictures, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thelow-contrast attribute.

The analyzer may analyze image data including at least one title areaand at least one body-part area, classify a corresponding one of theplurality of unit areas into a body-part attribute indicating that theimage data represents a body part of an electronic document to beprocessed or a title attribute indicating that the image data representsa title of the electronic document;

the scalar quantization section may perform scalar quantization for theimage data of each of the plurality of unit areas using a predeterminedquantization coefficient characters, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thebody-part attribute, and perform scalar quantization for the image dataof each of the plurality of unit areas using a predeterminedquantization coefficient for a title, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thetitle attribute;

the encoder may encode the image data of each of the plurality of unitareas using an SNR progressive technique, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thebody-part attribute, and encode the image data of each of the pluralityof unit areas using a resolution progressive technique, in a case wherethe analyzer classifies the corresponding one of the plurality of unitareas into the title attribute; and

the post quantization section may perform post quantization for theimage data of each of the plurality of unit areas using a predeterminedquantization parameter for characters, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into thebody-part attribute, and perform post quantization for the image data ofeach of the plurality of unit areas using a predetermined quantizationparameter for a title, in a case where the analyzer classifies thecorresponding one of the plurality of unit areas into the titleattribute.

The analyzer may analyze image data including at least an inside-areaand outside-area of a frame of an electronic document which is enclosedby a ruled line, and classify a corresponding one of the plurality ofunit areas into an inside-area attribute indicating that the image datais inside the frame or an outside-area attribute indicating that theimage data is outside the frame;

the scalar quantization section may perform scalar quantization for theimage data of each of the plurality of unit areas using a predeterminedquantization coefficient for the inside-area of the frame, in a casewhere the analyzer classifies the corresponding one of the plurality ofunit areas into the inside-area attribute, and perform scalarquantization for the image data of each of the plurality of unit areasusing a predetermined quantization coefficient for the outside-area ofthe frame, in a case where the analyzer classifies the corresponding oneof the plurality of unit areas into the outside-area attribute;

the encoder may encode the image data of each of the plurality of unitareas using an SNR progressive technique, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into theinside-area attribute, and encode the image data of each of theplurality of unit areas using a resolution progressive technique, in acase where the analyzer classifies the corresponding one of theplurality of unit areas into the outside-area attribute; and

the post quantization section may perform post quantization for theimage data of each of the plurality of unit areas using a predeterminedquantization parameter for characters, in a case where the analyzerclassifies the corresponding one of the plurality of unit areas into theinside-area attribute, and perform post quantization for the image dataof each of the plurality of unit areas using a predeterminedquantization parameter for the outside-area, in a case where theanalyzer classifies the corresponding one of the plurality of unit areasinto the outside-area attribute.

In order to achieve the above object, according to the fourth aspect ofthe present invention, there is provided an image encoder comprising:

analyzing means for analyzing image data, and classifying a plurality ofunit areas of the image data into a plurality of attributes;

encoding means for encoding image data of each of the plurality of unitareas using a corresponding one of a plurality of progressivetechniques, in accordance with a corresponding attribute classified bythe analyzing means; and

storage means for storing the image data encoded by the encoding meansin unit of each unit area.

According to this invention, the analyzing means analyzes image data(e.g. bitmap data), and classifies a plurality of unit areas (tiles) ofthe image data into a plurality of attributes. The encoding meansencodes image data of each of the plurality of unit areas using acorresponding one of a plurality of progressive techniques (the SNRprogressive technique and the resolution progressive technique), inaccordance with a corresponding attribute classified by the analyzingmeans. The storage means stores the image data encoded by the encodingmeans in unit of each unit area. Thus encoded image data is decodedusing a corresponding progressive technique, based on the attribute ofeach unit area. For example, in the case where the attribute of acorresponding one of the plurality of unit areas is the characterattribute, the data of the corresponding unit area is decoded using theSNR progressive technique. On the contrary, in the case where attributeis the picture attribute, the data of the corresponding unit area isdecoded using a resolution progressive technique. Hence, in the image tobe displayed on a predetermined display device, characters can berecognized by the user, before the data is completely decoded using theSNR progressive technique. On the other hand, pictures in the image canbe recognized by the user, before the data is completely decoded usingthe resolution progressive technique. In this manner, an electronicdocument is encoded in consideration of the human recognitioncharacteristics, so that users can easily recognize a target electronicdocument and that the document can rapidly be displayed.

In order to achieve the above object, according to the fifth aspect ofthe present invention, there is provided an image encoding methodcomprising:

analyzing image data, and classifying a plurality of unit areas of theimage data into a plurality of attributes;

encoding image data of each of the plurality of unit areas using acorresponding one of a plurality of progressive techniques, inaccordance with a corresponding attribute classified at the analyzing;and

storing the image data encoded at the encoding in unit of each unitarea, in a predetermined storage section.

According to this invention, the analyzing may include analyzing imagedata (e.g. bitmap data), and classifying a plurality of unit areas(tiles) of the image data into a plurality of attributes (e.g. acharacter attribute and a picture attribute). The encoding may includeencoding image data of each of the plurality of unit areas using acorresponding one of a plurality of progressive techniques, inaccordance with a corresponding attribute classified at the analyzing.The storing may include storing the image data encoded at the encodingin unit of each unit area, in a predetermined storage section. Thusencoded image data is decoded using a corresponding progressivetechnique, based on the attribute of each unit area. For example, in thecase where the attribute of a corresponding one of the plurality of unitareas is the character attribute, the data of the corresponding unitarea is decoded using the SNR progressive technique. On the contrary, inthe case where attribute is the picture attribute, the data of thecorresponding unit area is decoded using a resolution progressivetechnique. Hence, in the image to be displayed on a predetermineddisplay device, characters can be recognized by the user, before thedata is completely decoded using the SNR progressive technique. On theother hand, pictures in the image can be recognized by the user, beforethe data is completely decoded using the resolution progressivetechnique. In this manner, an electronic document is encoded inconsideration of the human recognition characteristics, so that userscan easily recognize a target electronic document and that the documentcan rapidly be displayed.

In order to achieve the above object, according to the sixth aspect ofthe present invention, there is provided an image encoding methodcomprising:

analyzing image data, and classifying a plurality of unit areas of theimage data into a plurality of attributes;

encoding image data of each of the plurality of unit areas using acorresponding one of a plurality of progressive techniques, inaccordance with a corresponding attribute classified at the analyzing;and

storing the image data encoded at the encoding in unit of each unitarea, in a predetermined storage section.

According to this invention, the analyzing may include analyzing imagedata (e.g. bitmap data), and classifying a plurality of unit areas(tiles) of the image data into a plurality of attributes (e.g. acharacter attribute and a picture attribute). The encoding may includeencoding image data of each of the plurality of unit areas using acorresponding one of a plurality of progressive techniques (e.g. the SNRprogressive technique and the resolution progressive technique), inaccordance with a corresponding attribute classified at the analyzing.The storing may include storing the image data encoded at the encodingin unit of each unit area, in a predetermined storage section. Thusencoded image data is decoded using a corresponding progressivetechnique, based on the attribute of each unit area. For example, in thecase where the attribute of a corresponding one of the plurality of unitareas is the character attribute, the data of the corresponding unitarea is decoded using the SNR progressive technique. On the contrary, inthe case where attribute is the picture attribute, the data of thecorresponding unit area is decoded using a resolution progressivetechnique. Hence, in the image to be displayed on a predetermineddisplay device, characters can be recognized by the user, before thedata is completely decoded using the SNR progressive technique. On theother hand, pictures in the image can be recognized by the user, beforethe data is completely decoded using the resolution progressivetechnique. In this manner, an electronic document is encoded inconsideration of the human recognition characteristics, so that userscan easily recognize a target electronic document and that the documentcan rapidly be displayed.

The encoding may include:

-   -   encoding, in a case where a corresponding one of the plurality        of unit areas is classified into the character attribute by the        analyzing, image data of the corresponding one of the plurality        of unit areas using an SNR progressive technique; and    -   encoding, in a case where the corresponding one of the plurality        of unit areas is classified into the picture attribute by the        analyzing, image data of the corresponding one of the plurality        of unit areas using a resolution progressive technique.

In order to achieve the above object, according to the seventh aspect ofthe present invention, there is provided an image encoding methodcomprising:

analyzing image data including at least one character area and at leastone picture area, and classifying a plurality of unit areas into acharacter attribute indicating that the image data is in the characterarea or a picture attribute indicating that the image data is in thepicture area;

performing scalar quantization for image data of each of the pluralityof unit areas using a corresponding one of two quantizationcoefficients, in accordance with whether the image data is classifiedinto the character attribute or the picture attribute at the analyzing;

encoding the image data of each of the plurality of unit areas which isquantized at the performing scalar quantization using a correspondingone of two progressive techniques, in accordance with whether the imagedata is classified into the character attribute or the picture attributeat the analyzing;

performing post quantization for the image data of each of the pluralityof unit areas which is encoded at the encoding using a corresponding oneof two quantization parameters, in accordance with whether the imagedata is classified into the character attribute or the picture attributeat the analyzing; and

storing the image data of each of the plurality of unit areas which ispost quantized at the performing post quantization, in a predeterminedstorage section.

According to this invention, the analyzing may include analyzing imagedata including at least one character area and at least one picturearea, and classifying a plurality of unit areas into a characterattribute indicating that the image data is in the character area or apicture attribute indicating that the image data is in the picture area.The performing scalar quantization may include performing scalarquantization for image data of each of the plurality of unit areas usinga corresponding one of two quantization coefficients, in accordance withwhether the image data is classified into the character attribute or thepicture attribute at the analyzing. The encoding may include encodingthe image data of each of the plurality of unit areas which is quantizedat the performing scalar quantization using a corresponding one of twoprogressive techniques, in accordance with whether the image data isclassified into the character attribute or the picture attribute at theanalyzing. The performing post quantization may include performing postquantization for the image data of each of the plurality of unit areaswhich is encoded at the encoding using a corresponding one of twoquantization parameters, in accordance with whether the image data isclassified into the character attribute or the picture attribute at theanalyzing. The storing may include storing the image data of each of theplurality of unit areas which is post quantized at the performing postquantization, in a predetermined storage section. Thus encoded imagedata is decoded using a corresponding progressive technique, based onthe attribute of each unit area. For example, in the case where theattribute of a corresponding one of the plurality of unit areas is thecharacter attribute, the data of the corresponding unit area is decodedusing the SNR progressive technique. On the contrary, in the case whereattribute is the picture attribute, the data of the corresponding unitarea is decoded using a resolution progressive technique. Hence, in theimage to be displayed on a predetermined display device, characters canbe recognized by the user, before the data is completely decoded usingthe SNR progressive technique. On the other hand, pictures in the imagecan be recognized by the user, before the data is completely decodedusing the resolution progressive technique. In this manner, anelectronic document is encoded in consideration of the human recognitioncharacteristics, so that users can easily recognize a target electronicdocument and that the document can rapidly be displayed.

The performing scalar quantization may include performing scalarquantization for the image data of each of the plurality of unit areasusing a predetermined quantization coefficient for characters, in a casewhere a corresponding one of the plurality of unit areas is classifiedinto the character attribute at the analyzing, and performing scalarquantization for the image data of each of the plurality of unit areasusing a predetermined quantization coefficient for pictures, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the picture attribute at the analyzing;

the encoding may include encoding the image data of each of theplurality of unit areas using an SNR progressive technique, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the character attribute at the analyzing, and encoding the imagedata of each of the plurality of unit areas using a resolutionprogressive technique, in a case where the corresponding one of theplurality of unit areas is classified into the picture attribute at theanalyzing; and

the performing post quantization section may include performing postquantization for the image data of each of the plurality of unit areasusing a predetermined quantization parameter for characters, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the character attribute at the analyzing, and performing postquantization for the image data of each of the plurality of unit areasusing a predetermined quantization parameter for pictures, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the picture attribute at the analyzing.

The analyzing may include analyzing the image data including the atleast one character area and at least one picture area in accordancewith whether the image data represents a high-contrast image or alow-contrast image, classifying a corresponding one of the plurality ofunit areas into an high-contrast attribute indicating that the imagedata represents the high-contrast image or a low-contrast attributeindicating that the image data representing the low-contrast image;

the performing scalar quantization may include performing scalarquantization for the image data of each of the plurality of unit areasusing a predetermined quantization coefficient for characters in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the high-contrast attribute at the analyzing, and performing scalarquantization for the image data of each of the plurality of unit areasusing a predetermined quantization coefficient for pictures, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the low-contrast attribute at the analyzing;

the encoding may include encoding the image data of each of theplurality of unit areas using an SNR progressive technique, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the high-contrast attribute at the analyzing, and encoding theimage data of each of the plurality of unit areas using a resolutionprogressive technique, in a case where the corresponding one of theplurality of unit areas is classified into the low-contrast attribute atthe analyzing; and

the performing post quantization may include performing postquantization for the image data of each of the plurality of unit areasusing a predetermined post quantization parameter for characters, in acase where the corresponding one of the plurality of unit areas isclassified into the high-contrast attribute at the analyzing, andperforming post quantization for the image data of each of the pluralityof unit areas using a predetermined post quantization parameter forpictures, in a case where the corresponding one of the plurality of unitareas is classified into the low-contrast attribute at the analyzing.

The analyzing may include analyzing image data including at least onetitle area and at least one body-part area, classifying a correspondingone of the plurality of unit areas into a body-part attribute indicatingthat the image data represents a body part of an electronic document tobe processed or a title attribute indicating that the image datarepresents a title of the electronic document;

the performing scalar quantization section may include performing scalarquantization for the image data of each of the plurality of unit areasusing a predetermined quantization coefficient characters, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the body-part attribute at the analyzer, and performing scalarquantization for the image data of each of the plurality of unit areasusing a predetermined quantization coefficient for a title, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the title attribute at the analyzing;

the encoding may include encoding the image data of each of theplurality of unit areas using an SNR progressive technique, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the body-part attribute at the analyzing, and encoding the imagedata of each of the plurality of unit areas using a resolutionprogressive technique, in a case where the corresponding one of theplurality of unit areas is classified into the title attribute at theanalyzing; and

the performing post quantization section may include performing postquantization for the image data of each of the plurality of unit areasusing a predetermined quantization parameter for characters, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the body-part attribute at the analyzing, and performing postquantization for the image data of each of the plurality of unit areasusing a predetermined quantization parameter for a title, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the title attribute at the analyzing.

The analyzing may include analyzing image data including at least aninside-area and outside-area of a frame of an electronic document whichis enclosed by a ruled line, and classifying a corresponding one of theplurality of unit areas into an inside-area attribute indicating thatthe image data is inside the frame or an outside-area attributeindicating that the image data is outside the frame;

the performing scalar quantization section may include performing scalarquantization for the image data of each of the plurality of unit areasusing a predetermined quantization coefficient for the inside-area ofthe frame, in a case where the corresponding one of the plurality ofunit areas is classified into the inside-area attribute at theanalyzing, and performing scalar quantization for the image data of eachof the plurality of unit areas using a predetermined quantizationcoefficient for the outside-area of the frame, in a case where thecorresponding one of the plurality of unit areas is classified into theoutside-area attribute at the analyzing;

the encoding may include encoding the image data of each of theplurality of unit areas using an SNR progressive technique, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the inside-area attribute at the analyzing, and encoding the imagedata of each of the plurality of unit areas using a resolutionprogressive technique, in a case where the corresponding one of theplurality of unit areas is classified into the outside-area attribute atthe analyzing; and

the performing post quantization section may include performing postquantization for the image data of each of the plurality of unit areasusing a predetermined quantization parameter for characters, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the inside-area attribute at the analyzing, and performing postquantization for the image data of each of the plurality of unit areasusing a predetermined quantization parameter for the outside-area, in acase where the corresponding one of the plurality of unit areas isclassified into the outside-area attribute at the analyzing.

In order to achieve the above object, according to the eighth aspect ofthe present invention, there is provided a computer readable recordingmedium which records a program for controlling a computer to execute animage encoding method comprising:

analyzing image data, and classifying a plurality of unit areas of theimage data into a plurality of attributes;

encoding image data of each of the plurality of unit areas using acorresponding one of a plurality of progressive techniques, inaccordance with a corresponding attribute classified at the analyzing;and

storing the image data encoded at the encoding in unit of each unitarea, in a predetermined storage section.

In order to achieve the above object, according to the ninth aspect ofthe present invention, there is provided a computer data signal embodiedin a carrier wave and representing an instruction sequence forcontrolling a computer to execute an image encoding method comprising:

-   -   analyzing image data, and classifying a plurality of unit areas        of the image data into a plurality of attributes;

encoding image data of each of the plurality of unit areas using acorresponding one of a plurality of progressive techniques, inaccordance with a corresponding attribute classified at the analyzing;and

storing the image data encoded at the encoding in unit of each unitarea, in a predetermined storage section.

BRIEF DESCRIPTION OF THE DRAWINGS

The object and other objects and advantages of the present inventionwill become more apparent upon reading of the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a block diagram showing an example of the structure of animage encoder according to each of the first to fourth embodiments ofthe present invention;

FIG. 2 is a block diagram showing an example of the specific structureof a processor included in the image encoder of FIG. 1;

FIG. 3 is a flowchart for explaining an encoding process which iscarried out by the image encoder according to the first embodiment ofthe present invention;

FIG. 4 is an exemplary diagram showing an example of a paper documentincluding both a character area and a picture (data except characters)area;

FIG. 5 is an exemplary diagram for explaining the state of bitmap datathat is classified into character areas and picture area as a result oflayout analysis;

FIG. 6 is an exemplary diagram for explaining the state of the bitmapdata wherein each area is divided into a plurality of tiles;

FIG. 7 is a flowchart for explaining an encoding process which iscarried out by the image encoder according to the second embodiment ofthe present invention;

FIG. 8 is a flowchart for explaining an encoding process which iscarried out by the image encoder according to the third embodiment ofthe present invention; and

FIG. 9 is a flowchart for explaining an encoding process which iscarried out by the image encoder according to the fourth embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be specificallybe explained with reference to the accompanying drawings. Note that thestandard of JPEG (Joint Picture Expert Group) 2000 is used in thepreferred embodiments of the present invention.

Explanations will now be made to a progressive transmission techniquewhich is employed in the embodiments of the present invention.

The progressive transmission technique is a method of transmitting anddisplaying a low-quality image whose resolution, gradation and frequencybandwidth are not initially in a sufficient level. According to such aprogressive transmission technique, subsequently, additional informationis gradually transmitted piece by piece to improve the quality of theimage, and then the image with the best quality can be transmitted anddisplayed.

According to the JPEG2000 (part1) standard, there are five progressiveprocedures each including a combination of: a resolution level; theprecinct (position); the component; and the layer, in a predeterminedorder. An SNR (Signal to Noise Ratio progressive) transmission techniqueand a resolution progressive technique will now be described.

The SNR progressive technique includes aLayer-Resolution-Component-Position (LRCP) progressive procedure, forencoding data from the most significant bit plane. If an image isdisplayed using the SNR progressive transmission technique, the usersees the image and notices that the image having agradually-increasing-number of colors is displayed.

In the case where an electronic document including both character dataand picture data (data excluding character data) is displayed using theSNR progressive transmission technique, the picture can not berecognized until the required colors are visualized appear, because itis necessary to identify the middle tones of the image. On the otherhand, since the edges of the characters are emphasized, characters canbe recognized even before the colors are not completely visualized.

The resolution progressive technique includes anResolution-Layer-Component-Position (RLCP) progressive procedure, forperforming encoding gradually from a low resolution level, usingmulti-resolution processing of wavelet transformation. Note, accordingto this technique, that an image is compressed in accordance with thedetail and roughness of dots of the image. In the case where the imageis displayed using the resolution progressive technique, the resolutionof the image gradually increases from a low resolution level, so thatthe user recognizes that the image gradually gets in focus from itsout-of-focus state.

In the case where the electronic document including both the characterdata and picture data (data excluding characters) is displayed using theresolution progressive technique, the picture can briefly be recognized,even if the picture is somehow out of focus. On the other hand, thecharacters can not be recognized, unless they are highly in focus.

An image encoder according to embodiments of the present inventiondisplays electronic documents including both character data and picturedata (data excluding characters), using the features of theabove-described progressive techniques. That is, the image encodertransmits and displays the character data included in the character areausing the SNR progressive technique, and transmits and displays pictureinformation included in the picture area using the resolutionprogressive technique. By this, the user can easily recognize thecontents of the transmission electronic documents, even before they arecompletely displayed (transmitted).

A quantization technique which is used in the preferred embodiments willnow be described. In the JPEG2000 standard, quantization is performedfor reducing the dynamic range of coefficients. In the JPEG2000standard, there are defined two kinds of quantization, such as scalarquantization and post quantization.

The scalar quantization is carried out for wavelet-transformedcoefficients, to achieve high-efficiency compression. This well-knownscalar quantization is done in the unit of pixels, and variousquantization techniques have been proposed.

The image encoder of the embodiments sets a coefficient (≧1) specifyingthe quantization step size, in accordance with whether the target datato be scalar quantized is character data or picture data, and performquantization in conformity with the target data. Specifically, in thecase of character data, the image encoder quantizes the target datausing a small coefficient, such as a predetermined value around “1”,etc. That is, the image encoder performs the quantization at a lowcompression ratio. In an extreme example, the quantization is notperformed, in the case where the target data to be quantized ischaracter data, (i.e., a coefficient “1” is used).

In the case where the target data to be quantized is picture data, theimage encoder quantizes the target data using a large coefficient, i.e.compresses the data using a high compression ratio. In the case ofpicture data, even if the target data is compressed using a highcompression ratio, the data can be processed in a preferable mannerwithout being seriously influenced by the high compression ratio.

The post quantization is achieved, by discarding the least significantbit plane of a complete form of a code string, in the context that thebit plane is encoded after the quantization.

In the scalar quantization, it is necessary to perform encoding whileappropriately changing the quantization step size, in order to controlan amount of predetermined data.

In the post quantization, the quantization is performed for the codestring after encoded, there is no need to perform encoding again. Thepost quantization has the characteristic that controlling of the amountof data can be realized in a single path.

The image encoder according to the embodiments of the present inventionsets a parameter (≧1) in accordance with whether the target data to bepost quantized is character data or picture data, and performquantization suitably and in conformity with the target data.Specifically, the image encoder sets a small parameter in the case ofthe picture data, thereby discarding very few bit planes, and achievesthe quantization. In an extreme example, the quantization is notperformed (sets “1” as a parameter), in the case where the target datais picture data.

On the other hand, in the case where the target data is character data,quantization is performed while setting a large value as a parameter. Inthis case, a greater amount of information is discarded than the case ofthe picture data, however, the character data can be processed in apreferable manner without being seriously influenced by the set largevalue as a parameter.

First Embodiment

The structure of an image encoder according to the first embodiment ofthe present invention will now be described.

FIG. 1 is a block diagram showing the schematic structure of the imageencoder of this embodiment. As shown in FIG. 1, the image encodercomprises a processor 10, a scanner 11, a storage device 12 and adisplay device 13.

The processor 10 includes a computer, such as a personal computer, aworkstation, a general computer, etc. In the case where the imageencoder of this embodiment is an incorporated device, such as amultifunction facsimile device or a multifunction device including amultifunction device and a printer, the processor 10 may include aninternally-installed CPU (Central Processing Unit) or an LSI (LargeScale Integration) only for image encoding.

The processor 10 controls the entire section of the image encoder.Specifically, the processor 10 is configured to include, as shown inFIG. 2, a bitmap data generator 110, a layout analyzer 120, an areadivider 130, an area determiner 140, a quantization section 150, anencoder 160, a post quantization section 170, and a temporary-storagesection 180.

The bitmap data generator 110 generates bitmap data based on imagesignals sent from the scanner 11. The bitmap data generator 110 storesthe generated bitmap data in the temporary-storage section 180.

The layout analyzer 120 performs layout analysis based on the bitmapdata stored in the temporary-storage section 180, and classifies piecesof the bitmap data into a character area and a picture (for data exceptcharacter data) area.

The area divider 130 divides each of the character area and the picturedata into a plurality of tiles (unit area).

The area determiner 140 determines whether each of the plurality oftiles is in the character area or the picture area.

The quantization section 150 performs the scalar quantization forcharacters or for pictures, in accordance with the determination of thearea determiner 140. Note that the quantization section 150 performs DWT(Discrete Wavelet Transformation) before performing the scalarquantization.

The encoder 160 performs encoding for each tile, using the SNRprogressive technique or the resolution progressive technique inaccordance with the determination of the area determiner 140.

The post quantization section 170 performs post quantization for eachtile, using a quantization parameter for characters or a quantizationparameter for pictures in accordance with the determination of the areadeterminer 140.

The temporary-storage section 180 includes a work memory, andtemporarily stores the bitmap data generated by the bitmap datagenerator 110.

Operations of the above-described processor 10 will more specifically bedescribed with reference to an encoding process, as will be describedlater.

The scanner 11 scans the characters, symbols, figures, pictures, etc.which are printed on a paper medium, etc., and sends resultant imagesignals acquired as a result of the scanning to the processor 10.

The storage device 12 stores encoded data (encoded electronic document)supplied from the processor 10. The encoded stored in this storagedevice 12 is read out by the processor 10, and supplied to the displaydevice 13.

Upon reception of the encoded data, the display device 13 reproduces anddisplays an electronic document based on encoded data supplied from theprocessor 10. The display device 13 and the processor 10 may be directlyconnected with each other through a wire, in a wireless manner, orthrough a network, such as a public line or the Internet.

Operations of the image encoder according to the first embodiment of thepresent invention will now be explained with reference to FIG. 3.

FIG. 3 is a flowchart for explaining the encoding process executed bythe image encoder of this embodiment.

The scanner 11 scans a target paper document to be digitized (Step S10).That is, the scanner 11 scans a paper document including both thecharacters and pictures (information except characters), as that shownin FIG. 4. The scanner 11I sends image signals obtained as a result ofthis scanning, to the processor 10.

The processor 10 generates bitmap data from the sent image signals (StepS11). The processor 10 temporarily stores the generated bitmap data inits internal work memory (the temporary storage section 180).

The processor 10 performs layout analysis of the document, based on thebitmap data stored in the work memory using the OCR (Optical CharacterRecognition) technique (Step S12). As a result of this layout analysis,pieces of the bitmap data are classified into the character area and thepicture area.

For example, as shown in FIG. 5, the pieces of the bitmap data areclassified into three areas of: a picture area “P”, a character area“C1” and a character area “C2”. The processor 10 sets the attribute ofeach area as “Character” or “Picture (data except characters)”. Any ofthe attributes is affixed to a corresponding encoded electronicdocument.

The processor 10 divides each of the above-described areas into aplurality of tiles, as a pre-process for performing encoding in theJPEG2000 standard (Step S13). FIG. 6 shows an example of tile-division.As shown in FIG. 6, the picture area “P” is divided into six tiles T,the character area “C1” is divided into eight tiles T, and the characterarea “C2” is divided into six tiles T. The size of each tile T is thesame.

The tile-dividing method and the shape of the tiles are not limited tothe exemplary case of FIG. 6, and are arbitrary (any of varioustile-dividing methods and any of various shapes can be used).

Referring back to FIG. 3, the processor 10 affixes analysis informationto each tile (the bitmap data included in each tile) (Step S14). Notethat the analysis information expresses, for example, “0” as a characterand “1” as a picture.

For example, the processor 10 creates a table including a predeterminednumber of data items which is the same as the number of tiles of imagedata, and affixes the analysis information to the table in associationwith the tile numbers. In this case, the tile numbers are a kind ofparameters, of SOT marker segments defined in the JPEG2000 standard, andare numbers assigned in the raster order from “0”. The processor 10creates a table including the analysis information in association witheach tile number, and stores the created table in the internal workmemory (the temporary storage section 180).

The processor 10 refers to one tile from the work memory, and determineswhether the attribute of the tile is “Character” (Step S15). That is,the processor 10 performs the determination of the attribute, byreferring to the above-described table.

In the case where the attribute of the tile is “Character”, theprocessor 10 performs DWT for the tile, and carries out the scalarquantization for characters (Step S16). During this DWT, the processor10 transforms the data of the tile into a plurality of coefficients.After this, the processor 10 performs the scalar quantization for thecoefficients obtained as a result of the transformation, using aquantization coefficient for characters. In this case, the quantizationcoefficient for characters is such a value that the quantization can notbe performed or such a small value that data compression is performed ata low compression ratio.

The processor 10 encodes the obtained coefficients using the SNRprogressive technique (Step S17). The specific encoding method may beset with reference to the description of the SNR progressive techniqueaccording to the above-described JPEG2000 standard of the specificationof the JPEG2000 standard.

The processor 10 performs the post quantization using the quantizationparameter for characters, for the encoded data (Step S18). In this case,as the quantization parameter for characters, a parameter of a largevalue is used so that data compression is performed at a highcompression ratio. As a result of the encoding and quantization, it ispossible to control the amount of data to be encoded and the imagequality of data which are included in those “Character” tiles. Thiscontrolling can be achieved without influencing of the viewing by theuser.

In the above-described step S15, in the case where it is determined thatthe attribute of the tile is not “Character”, i.e. the attribute is“Picture”, the processor 10 performs the DWT for the tile and performsscalar quantization for pictures (Step S19). That is, the processor 10transforms the data in the tile into a plurality of coefficients usingthe DWT technique. After this, the processor 10 performs scalarquantization using a quantization coefficient for pictures, for theresultant coefficients. In this case, the quantization coefficient forpictures is such a large value that data compression is performed at ahigh compression ratio.

The processor 10 encodes the quantized coefficients using a resolutionprogressive technique (Step S20). The specific encoding method may beset with reference to the description of the SNR progressive techniqueaccording to the above-described JPEG2000 standard of the specificationof the JPEG2000 standard.

The processor 10 performs post quantization for the encoded data, usinga quantization parameter for pictures (Step S21). In this case, thequantization parameter for pictures is such a small value that datacompression is achieved at a low compression ratio. That is, thequantization parameter for pictures is smaller than that for characters.As a result of the encoding and quantization, it is possible to controlthe amount of data to be encoded and the image quality of data which areincluded in the “Picture” tiles, without influencing the viewing by theuser.

The processor 10 stores the encoded data quantized in theabove-described step S18 or the step S21, in the storage device 12 (StepS22).

The processor 10 executes the procedures of the above-described stepsS15 to S22, for each of the plurality of tiles. In the case where it isdetermined the attribute of a target tile is “Character”, the processor10 encodes the data in the tile using the SNR progressive technique. Onthe contrary, in the case where it is determined that the attribute of acorresponding tile is “Picture”, the processor 10 encodes the data inthe tile using the resolution progressive technique. After the encoding,the processor 10 stores thus encoded electronic document in the storagedevice 12.

After this, the processor 10 decodes thus encoded electronic documentstored in the storage device 12 and displays the decoded document on thedisplay device, in response to a request therefor from the user. At thistime, the processor 10 decodes the electronic document using acorresponding progressive technique, based on the attribute of eachtile. That is, the processor 10 performs the decoding using the SNRprogressive technique, in the case where the attribute of a target tileis “Character”. On the contrary, the processor 10 performs the decodingusing the resolution progressive technique, in the case where theattribute of a target tile is “Picture”.

As a result of the above, in the electronic document to be displayed onthe display device 13, those characters can be recognized by the userbefore the data is completely decoded using the SNR progressivetechnique, and those pictures can be recognized by the user before thedata is completely decoded using the resolution progressive technique.

As described above, the image encoder according to the first embodimentof the present invention encodes the electronic document, usingdifferent progressive techniques in the character area and the picturearea. That is, the SNR progressive technique is employed in thecharacter area, while the resolution progressive technique is employedin the picture area.

Hence, when decoding the encoded electronic document, suitable decodingtechniques can be employed for the characters and pictures,respectively. As a result of this, the user can soon recognize thecontents of the electronic document including both characters andpictures (information except characters).

In the encoding process, the encoded data is compressed using the postquantization technique, the amount of data to be encoded can easily becontrolled. Particularly, in the character area, data compression can beachieved at a higher compression ratio than that in the picture area,using the post quantization. Hence, an electronic document including alarge number of characters (a wide range of character area) can rapidlybe transmitted and displayed.

In the above-described first embodiment, the explanations have been madeto the image encoder, in the case where attribute information is affixedto each tile in association with each other. However, information,representing a selection manner for suitably adapting a progressivetechnique to/from another progressive technique, may be affixed to eachof the plurality of tiles. In this case, it is not necessary to preparea table storing information regarding the tiles and their attributes inassociation with each other, and hence simplifying the structure orprocessing procedures of the image encoder.

In the above-described first embodiment, the image encoder has beenexplained, in the case where both of the SNR progressive technique andthe resolution progressive technique are employed for displaying andtransmitting the data. However, any other progressive techniques may beused in a manner corresponding to the characters and pictures of thetiles. For example, of five progressive procedures defined in theJPEG2000 (part1, etc.), an arbitrary procedure may be employed, or anyother suitable progressive technique may be used.

Second Embodiment

An image encoder according to the second embodiment of the presentinvention will now be described. The image encoder of the secondembodiment has the same structure as that described in the firstembodiment shown in FIG. 1.

One feature of the image encoder according to the second embodiment ofthe present invention is that a suitable progressive technique isselected and adapted in accordance with the contrast level in theelectronic document. Specifically, the processor 10 performs layoutanalysis, and selects one of the SNR progressive technique and theresolution progressive technique, in accordance with the contrast levelin the document.

Operations of the image encoder according to the second embodiment ofthe present invention will now be described with reference to FIG. 7.

FIG. 7 is a flowchart for explaining an encoding process which iscarried out by the image encoder of the second embodiment. In theencoding process of FIG. 7, the same (or corresponding) procedures asthose of the encoding process in the case of the first embodiment aredenoted by the same reference numerals as those shown in FIG. 3.

The scanner 11 scans a target paper document to be digitized (Step S10),and sends image signals obtained by the scanning to the processor 10.

The processor 10 generates bitmap data from the sent image signals (StepS11), and performs the layout analysis based on the generated bitmapdata (Step S12). That is, the processor 10 performs the layout analysis,on the basis of the contrast level in the document. As a result of thislayout analysis, the character area is classified into a “high-contrastarea”, whereas the picture area is classified into a “low-contrastarea”.

The processor 10 divides each of the above areas into a plurality oftiles (Step S13), and affixes analysis information to each tile (bitmapdata included in each tile) (Step S14).

The processor 10 creates analysis information defining “0” as ahigh-contrast area and “1” as a low-contrast area in association witheach tile number, and stores the created table in the internal workmemory (the temporary storage section 180).

The processor 10 refers to one tile from the work memory, and determineswhether this tile is in the high-contrast area (Step S30). Thisdetermination is made, every time the processor 10 refers theabove-described table.

In the case where it is determined that the tile is in the high-contrastarea, the processor 10 performs the DWT and the scalar quantization forcharacters for this tile (Step S16). That is, likewise the firstembodiment, the processor 10 performs the DWT for the data included inthe tile, thereby transforming the data into a plurality ofcoefficients, and performs scalar quantization for the obtainedcoefficients using a quantization coefficient for characters. In thiscase, the quantization coefficient is the same as that described in thefirst embodiment.

The processor 10 encodes the quantized coefficients using the SNRprogressive technique (S17), and performs post quantization for theencoded data using a quantization parameter for characters (Step S18).The quantization parameter for characters is also the sane as thatdescribed in the first embodiment.

In the above-described step S30, in the case where it is determined thatthe tile is not in the high-contrast area (in the low-contrast area),the processor 10 performs the DWT and the scalar quantization forpictures for this tile (Step S19). Likewise the case of the firstembodiment, the processor 10 performs DWT for the data included in thetile, thereby transforming the data into a plurality of coefficients.After this, the processor 10 performs scalar quantization for theobtained coefficients using a quantization coefficient for pictures.This quantization coefficient for pictures is also the same as thatdescribed in the first embodiment.

The processor 10 encodes the quantized coefficients using the resolutionprogressive technique (Step S20), and performs post quantization for theencoded data using the quantization parameter for pictures (Step S21).The quantization parameter for pictures is the same as that described inthe first embodiment.

The processor 10 stores the encoded data quantized in theabove-described step S18 and the step S21 in the storage device 12 (StepS22).

The processor 10 executes the procedures of the above steps S30 to S22for each of the plurality of tiles. That is, in the case where it isdetermined that a target tile is in the high-contrast area, theprocessor 10 encodes the data of the tile using the SNR progressivetechnique. On the contrary, in the case where it is determined that atarget tile is in the low-contrast area, the processor 10 encodes thedata of the tile using the resolution progressive technique. Then, theprocessor 10 stores thus encoded electronic document in the storagedevice 12.

After this, the processor 10 decodes the encoded electronic documentstored in the storage device 12 and displays the decoded document on thedisplay device 13, in response to a request therefor from the user. Atthis time, the processor 10 performs decoding using a suitableprogressive technique, in accordance with the contrast level of eachtile. That is, in the case where it is determined that the target tileis in the high-contrast area, the processor 10 assumes that the tile isin the character area, and decodes the data of the tile using the SNRprogressive technique. On the contrary, in the case where it isdetermined that the target tile is in the low-contrast area, theprocessor 10 assumes that the tile is in the picture area, and decodesthe data of the tile using the resolution progressive technique.

As a result of this, in the electronic document displayed on the displaydevice 13, those characters can sufficiently be recognized by the userbefore the data is completely decoded using the SNR progressivetechnique, and those pictures can sufficiently be recognized by the userbefore the data is completely decoded using the resolution progressivetechnique.

As described above, the image encoder according to the second embodimentof the present invention encodes the electronic document, usingdifferent progressive techniques in the high-contrast area (characterarea) and the low-contrast area (picture area). That is, the processor10 encodes data included in the character area using the SNR progressivetechnique, and encodes data included in the picture area using theresolution progressive technique.

When decoding the encoded electronic document, characters and picturescan be decoded using suitable decoding techniques, respectively. As aresult of this, the user can soon recognize the contents of theelectronic document including both the characters and pictures.

Third Embodiment

An image encoder according to the third embodiment of the presentinvention will now be explained. The image encoder of this embodimenthas the same structure as the structure of the image encoder accordingto the first embodiment which is shown in FIG. 1.

One feature of the image encoder of this embodiment is that a suitableprogressive technique is selected, in accordance with whether targetdata is a title or the body part of an electronic document.Specifically, the processor 10 performs the layout analysis inaccordance with whether the target data is a title or the body part ofthe electronic document. Based on the result of the analysis, theprocessor 10 employs the SNR progressive technique or the resolutionprogressive technique, for encoding the target data.

Operations of the image encoder according to the third embodiment of thepresent invention will now be explained with reference to FIG. 8.

FIG. 8 is a flowchart for explaining an encoding process which iscarried out by the image encoder of this embodiment. In the encodingprocess of FIG. 8, the same (or corresponding) procedures as those ofthe encoding process in the case of the first embodiment are denoted bythe same reference numerals as those shown in FIG. 3.

The scanner 11 scans a target paper document to the digitized (StepS10), and sends image signals obtained by the scanning to the processor10.

The processor 10 generates bitmap data from the sent image signals (StepS11), and performs layout analysis based on the bitmap data (Step S12).At this time, the processor 10 determines whether each piece of thebitmap data corresponds to the title or body part of the electronicdocument. As a result of this layout analysis, each piece of the bitmapdata is classified into a title area or a body area.

The processor 10 divides each of the title area and the body area into aplurality of tiles (Step S13), and affixes analysis information to eachtile (bitmap data included in each tile) (Step S14). Note that thisanalysis information defines, for example, “0” as the title area and “1”as the body area.

The processor 10 creates a table including the analysis information inassociation with tile numbers, and stores the created table in theinternal memory (temporary storage section 180).

The processor 10 refers one tile from the work memory, and determineswhether this tile is in the title area (Step S40). This determination ismade every time the processor 10 refers the above-described table.

In the case where it is determined that that the tile is not in thetitle area (i.e. is in the body area), the processor 10 performs the DWTand scalar quantization for characters, for this tile (Step S16). Thatis, likewise the first embodiment, the processor 10 transforms data ofthis tile into a plurality of coefficients, using the DWT, and thenperforms the scalar quantization for the obtained coefficients using aquantization coefficient for characters. The quantization coefficientfor characters is the same as that described in the first embodiment.

The processor 10 encodes the quantized coefficients using the SNRprogressive technique (Step S17). Generally, small characters are usedin the body part of the document, and thus it is preferred that the SNRprogressive technique be used for the characters in the body part.

The processor 10 performs post quantization for the encoded data using aquantization parameter for characters (Step S18). The quantizationparameter for character is the same as that described in the firstembodiment.

In the above-described step S40, in the case where it is determined thatthe target tile is included in the title area, the processor 10 performsthe DWT for this time, and performs scalar quantization for title (StepS41). Specifically, the processor 10 transforms the data of this tileinto a plurality of coefficients through the DWT, and performs scalarquantization for the obtained coefficients using a quantizationcoefficient for title. In this case, the quantization coefficient fortitle is such a large value that data compression is performed at a highcompression ratio, likewise the first embodiment.

The processor 10 encodes the quantized coefficients using the resolutionprogressive technique (Step S20). Generally, large characters are usedfor the title of a document, or colored illustrations are used for thetitle. Hence, it is preferred that the title be formed using theresolution progressive technique.

The processor 10 performs post quantization for the encoded data, usinga quantization parameter for title (Step S42). Likewise the firstembodiment, the quantization parameter for title is such a small valuethat data compression is achieved at a high compression ratio, likewisethe case of the first embodiment (the quantization parameter forpictures).

The processor 10 stores the encoded data which has been quantized in theabove-described steps S18 or S42, in the storage device 12 (Step S22).

The processor 10 carries out the procedures of the above-described stepsS40 to S22 for each of the plurality of tiles. Specifically, in the casewhere it is determined that the target tile is included in the bodyarea, the processor 10 encodes the data of the tile using the SNRprogressive technique. On the contrary, in the case where it isdetermined that the target tile is included in the title area, theprocessor 10 encodes the data of the tile using the resolutionprogressive technique. Then, the processor 10 stores thus encodedelectronic document in the storage device 12.

After this, the processor 10 decodes the electronic document stored inthe storage device 12 and displays the decoded document on the displaydevice 13, in response to a request therefor from the user. In the case,the processor 10 decodes such data using a suitable progressivetechnique, in accordance with whether each tile is included in the titlearea or in the body area. Specifically, the processor 10 decodes thedata of a target tile using the SNR progressive technique, in the casewhere it is determined that the tile is included in the body area. Onthe contrary, the processor 10 decodes the data of a target tile usingthe resolution progressive technique, in the case where it is determinedthat the tile is included in the title area.

Hence, in the electronic document to be displayed on the display device13, the body part of the document can be recognized by the user beforedata of the tiles included in the body area are completely decoded usingthe SNR progressive technique, whereas the title can be recognized bythe user before data of the tiles included in the title area arecompletely decoded using the resolution progressive technique.

As explained above, the image encoder according to the third embodimentof the present invention encodes an electronic document using differentprogressive techniques in the title area and the body area in thedocument. That is, the image encoder encodes data for the body areausing the SNR progressive technique, and encodes data for the title areausing the resolution progressive technique.

By this, when decoding the encoded electronic document, the title andbody part of the document can be decoded using suitable decodingtechniques, respectively. As a result of this, the user can soonrecognize the contents of the electronic document including both thetitle and the body part.

Fourth Embodiment

An image encoder according to the fourth embodiment of the presentinvention will now be described. The image encoder of this embodimenthas the same structure as the structure of the image encoder accordingto the first embodiment as shown in FIG. 1.

One feature of the image encoder of this embodiment is that a suitableprogressive technique is selected based on determination as to whether atarget data item is inside or outside the frame within an electronicdocument. Specifically, the processor 10 performs the layout analysis,based on the determination. After this, the processor 10 selects one ofthe SNR progressive technique and the resolution progressive technique,for encoding the target data item.

Operations of the image encoder according to the fourth embodiment ofthe present invention will now be described with reference to FIG. 9.

FIG. 9 is a flowchart for explaining an encoding process which iscarried out by the image encoder of this embodiment. In the encodingprocess of FIG. 9, the same (or corresponding) procedures as those ofthe encoding process in the case of the first embodiment are denoted bythe same reference numerals as those shown in FIG. 3.

The scanner 11 scans a target paper document to be digitized (Step S10)so as to obtain image signals, and sends the obtained image signals tothe processor 10.

The processor 10 generates bitmap data from the sent image signals (StepS11), and performs layout analysis, based on the bitmap data (Step S12).In this case, specifically, the processor 10 determines whether a targetdata item is inside or outside the frame which is enclosed by a ruledline, etc. As a result of this layout analysis, pieces of the bitmapdata are classified in an inside-area (inside the frame of the document)or an outside-area (outside the frame of the document).

The processor 10 divides each of the inside-area and the outside-areainto a plurality of tiles (Step S13), and affixes analysis informationto each of the tiles (bitmap data included in each tile) (Step S14).Note that this analysis information expresses that “0” as theinside-area and “1” as the outside-area.

The processor 10 creates a table including this analysis information inassociation with corresponding tile numbers, and stores the createdtable in the internal work memory (the temporary storage section 180).

The processor 10 refers to one tile from the work memory, and determineswhether this tile is inside the frame (Step S50). This determination ismade based on the information included in the above-described table.

In the case where it is determined that the tile is included in the areawithin the frame, the processor 10 performs the DWT and scalarquantization for characters (Step S16). That is, likewise the case ofthe first embodiment, the processor 10 transforms data of this time intoa plurality of coefficients, and performs scalar quantization for theobtained coefficients using a quantization coefficient for characters.The quantization coefficient for characters is the same as thatdescribed in the first embodiment.

The processor 10 encodes the quantized coefficients using the SNRprogressive technique (Step S17). For example, just like an accountbook, in the case where small characters are written in the frame of thedocument, it is preferred to encode the data using the SNR progressivetechnique.

The processor 10 performs post quantization for the obtained encodeddata, using a quantization parameter for characters (Step S18). Thequantization parameter for characters is the same as that described inthe first embodiment.

In the above-described step S50, in the case where it is determined thatthe tile is not within the frame (i.e. the tile is outside the frame),the processor 10 performs DWT for this time, and performs scalarquantization for the outside-area (Step S51). That is, the processor 10transforms data within this tile into coefficients, and performs scalarquantization for the obtained coefficients using a quantizationcoefficient for outside-area. In this case, the quantization coefficientis such a large value that data compression is achieved at a highcompression ratio.

The processor 10 encodes the quantized coefficients using the resolutionprogressive technique (Step S20) to obtain encoded data, and performspost quantization for the obtained encoded data using a quantizationparameter for outside-area (Step S52). This quantization parameter issuch a small value that data compression can be performed at a lowcompression ratio.

The processor 10 stores the encoded data which has been quantized in theabove-described step S18 or S52, in the storage device 12 (Step S22).

The processor 10 carries out the procedures of the above-described stepsS50 to S22 for each of the plurality of tiles. Specifically, theprocessor 10 encodes data of a target tile using the SNR progressivetechnique, in the case where it is determined that the tile is withinthe inside-area. On the contrary, the processor 10 encodes data of atarget tile using the resolution progressive technique, in the casewhere it is determined that the tile is within the outside-area. Then,the processor 10 stores thus encoded electronic document in the storagedevice 12.

After this, the processor 10 decodes the encoded electronic documentstored in the storage device 12 and displays the decoded document on thedisplay device 13, in response to a request therefor from the user. Atthis time, the processor 10 decodes the document using a correspondingprogressive technique, in accordance with whether each tile is inside oroutside the frame. That is, in the case where it is determined that atarget tile is within the frame, the processor 10 decodes data of thefile using the SNR progressive technique. On the contrary, in the casewhere it is determined that a target file is outside the frame, theprocessor 10 decodes data of the file using the resolution progressivetechnique.

Thus, in the electronic document displayed on the display device 13,those data within the frame can be recognized by the user before thedata is completely decoded using the SNR progressive technique. On thecontrary, those data outside the frame can be recognized by the userbefore the data is completely decoded using the resolution progressivetechnique.

As explained above, the image encoder according to the fourth embodimentof the present invention performs encoding of data using differentprogressive techniques in the inside-area and the outside-area. That is,the SNR progressive technique is used for encoding data inside theframe, while the resolution progressive technique is used for encodingdata outside the frame.

Hence, when decoding the encoded electronic document, suitable decodingtechniques can be employed for the data inside the frame and the dataoutside the frame, respectively. As a result of this, the user can soonrecognize the contents of the electronic document including both data ofthe inside-area and data of the outside-area (information exceptcharacters).

In the above-described first to fourth embodiments, the electronicdocument is encoded in accordance with the human recognitioncharacteristics, so that the electronic document can easily berecognized by the user and can be rapidly displayed. However, the imageencoder according to each of the first to fourth embodiments includes asearch function for searching a predetermined electronic document from amass of electronic documents. When generating an electronic document,according to this configuration, the image encoder according to each ofthe embodiments automatically sets at least one search keyword andaffixes this keyword to the electronic document.

For example, the processor 10 performs the layout analysis, whileperforming the optical character recognition, and extracts at least onekeyword from a corresponding electronic document during a predeterminedkeyword extraction process.

As a result of this keyword extraction process, the processor 10 canautomatically affixes the keyword (necessary for searching for apredetermined electronic document) to the electronic document.

In the above-described first to fourth embodiments, image signals areacquired obtained from a paper document by using the scanner 11.However, the method of acquiring the image signals is arbitrary. Forexample, a digital camera may be used for acquiring image signals.

The encoder of the present invention can be realized by a generalcomputer, without the need for a dedicated system. A program and datafor controlling a computer to execute the above-described processes maybe recorded on a medium (a floppy disk, CD-ROM, DVD or the like) anddistributed, and the program may be installed into the computer and runon an OS (Operating System) to execute the above-described processes,thereby achieving the encoder of the present invention. The aboveprogram and data may be stored in a disk device or the like in theserver device on the Internet, and embedded in a carrier wave. Theprogram and data embedded in the carrier wave may be downloaded into thecomputer so as to realize the encoder of the present invention.

Various embodiments and changes may be made thereonto without departingfrom the broad spirit and scope of the invention. The above-describedembodiments are intended to illustrate the present invention, not tolimit the scope of the present invention. The scope of the presentinvention is shown by the attached claims rather than the embodiments.Various modifications made within the meaning of an equivalent of theclaims of the invention and within the claims are to be regarded to bein the scope of the present invention.

This application is based on Japanese Patent Application No. 2001-209017filed on Jul. 10, 2001, and including specification, claims, drawingsand summary. The disclosure of the above Japanese Patent Application isincorporated herein by reference in its entirety.

1-3. (canceled)
 4. An image encoder comprising: an analyzer whichanalyzes image data including at least one character area and at leastone picture area, and classifies a plurality of unit areas into acharacter attribute indicating that the image data is in the characterarea or a picture attribute indicating that the image data is in thepicture area; a scalar quantization section which performs scalarquantization for image data of each of the plurality of unit areas usinga corresponding one of two quantization coefficients, in accordance withwhether said analyzer classifies the image data into the characterattribute or the picture attribute; an encoder which encodes the imagedata of each of the plurality of unit areas which is quantized by saidscalar quantization section using a corresponding one of two progressivetechniques, in accordance with whether said analyzer classifies theimage data into the character attribute or the picture attribute; a postquantization section which performs post quantization for the image dataof each of the plurality of unit areas which is encoded by said encoderusing a corresponding one of two quantization parameters, in accordancewith whether said analyzer classifies the image data into the characterattribute or the picture attribute; and a storage section which storesthe image data of each of the plurality of unit areas which is postquantized by said post quantization section.
 5. The image encoderaccording to claim 4, wherein: said scalar quantization section whichperforms scalar quantization for the image data of each of the pluralityof unit areas using a predetermined quantization coefficient forcharacters, in a case where said analyzer classifies a corresponding oneof the plurality of unit areas into the character attribute, andperforms scalar quantization for the image data of each of the pluralityof unit areas using a predetermined quantization coefficient forpictures, in a case where said analyzer classifies the corresponding oneof the plurality of unit areas into the picture attribute; said encoderencodes the image data of each of the plurality of unit areas using anSNR progressive technique, in a case where said analyzer classifies thecorresponding one of the plurality of unit areas into the characterattribute, and encodes the image data of each of the plurality of unitareas using a resolution progressive technique, in a case where saidanalyzer classifies the corresponding one of the plurality of unit areasinto the picture attribute; and said post quantization section performspost quantization for the image data of each of the plurality of unitareas using a predetermined quantization parameter for characters, in acase where said analyzer classifies the corresponding one of theplurality of unit areas into the character attribute, and performs postquantization for the image data of each of the plurality of unit areasusing a predetermined quantization parameter for pictures, in a casewhere said analyzer classifies the corresponding one of the plurality ofunit areas into the picture attribute.
 6. The image encoder according toclaim 4, wherein: said analyzer analyzes the image data including the atleast one character area and at least one picture area in accordancewith whether the image data represents a high-contrast image or alow-contrast image, classifies a corresponding one of the plurality ofunit areas into an high-contrast attribute indicating that the imagedata represents the high-contrast image or a low-contrast attributeindicating that the image data representing the low-contrast image; saidscalar quantization performs scalar quantization for the image data ofeach of the plurality of unit areas using a predetermined quantizationcoefficient for characters in a case where said analyzer classifies thecorresponding one of the plurality of unit areas into the high-contrastattribute, and performs scalar quantization for the image data of eachof the plurality of unit areas using a predetermined quantizationcoefficient for pictures, in a case where said analyzer classifies thecorresponding one of the plurality of unit areas into the low-contrastattribute; said encoder encodes the image data of each of the pluralityof unit areas using an SNR progressive technique, in a ease where saidanalyzer classifies the corresponding one of the plurality of unit areasinto the high-contrast attribute, and encodes the image data of each ofthe plurality of unit areas using a resolution progressive technique, ina case where said analyzer classifies the corresponding one of theplurality of unit areas into the low-contrast attribute; and said postquantization section performs post quantization for the image data ofeach of the plurality of unit areas using a predetermined postquantization parameter for characters, in a case where said analyzerclassifies the corresponding one of the plurality of unit areas into thehigh-contrast attribute, and performs post quantization for the imagedata of each of the plurality of unit areas using a predetermined postquantization parameter for pictures, in a case where said analyzerclassifies the corresponding one of the plurality of unit areas into thelow-contrast attribute.
 7. The image encoder according to claim 4,wherein: said analyzer analyzes image data including at least one titlearea and at least one body-part area, classifies a corresponding one ofthe plurality of unit areas into a body-part attribute indicating thatthe image data represents a body part of an electronic document to beencoded or a title attribute indicating that the image data represents atitle of the electronic document; said scalar quantization sectionperforms scalar quantization for the image data of each of the pluralityof unit areas using a predetermined quantization coefficient characters,in a case where said analyzer classifies the corresponding one of theplurality of unit areas into the body-part attribute, and performsscalar quantization for the image data of each of the plurality of unitareas using a predetermined quantization coefficient for a title, in acase where said analyzer classifies the corresponding one of theplurality of unit areas into the title attribute; said encoder encodesthe image data of each of the plurality of unit areas using an SNRprogressive technique, in a case where said analyzer classifies thecorresponding one of the plurality of unit areas into the body-partattribute, and encodes the image data of each of the plurality of unitareas using a resolution progressive technique, in a case where saidanalyzer classifies the corresponding one of the plurality of unit areasinto the title attribute; and said post quantization section performspost quantization for the image data of each of the plurality of unitareas using a predetermined quantization parameter for characters, in acase where said analyzer classifies the corresponding one of theplurality of unit areas into the body-part attribute, and performs postquantization for the image data of each of the plurality of unit areasusing a predetermined quantization parameter for a title, in a casewhere said analyzer classifies the corresponding one of the plurality ofunit areas into the title attribute.
 8. The image encoder according toclaim 4, wherein: said analyzer analyzes image data including at leastan inside-area and outside-area of a frame of an electronic documentwhich is enclosed by a ruled line, and classifies a corresponding one ofthe plurality of unit areas into an inside-area attribute indicatingthat the image data is inside the frame or an outside-area attributeindicating that the image data is outside the frame; said scalarquantization section performs scalar quantization for the image data ofeach of the plurality of unit areas using a predetermined quantizationcoefficient for the inside-area of the frame, in a case where saidanalyzer classifies the corresponding one of the plurality of unit areasinto the inside-area attribute, and performs scalar quantization for theimage data of each of the plurality of unit areas using a predeterminedquantization coefficient for the outside-area of the frame, in a casewhere said analyzer classifies the corresponding one or the plurality ofunit areas into the outside-area attribute; said encoder encodes theimage data of each of the plurality of unit areas using an SNRprogressive technique, in a case where said analyzer classifies thecorresponding one of the plurality of unit areas into the inside-areaattribute, and encodes the image data of each of the plurality of unitareas using a resolution progressive technique, in a case where saidanalyzer classifies the corresponding one of the plurality of unit areasinto the outside-area attribute; and said post quantization sectionperforms post quantization for the image data of each of the pluralityof unit areas using a predetermined quantization parameter forcharacters, in a case where said analyzer classifies the correspondingone of the plurality of unit areas into the inside-area attribute, andperforms post quantization for the image data of each of the pluralityof unit areas using a predetermined quantization parameter for theoutside-area, in a case where said analyzer classifies the correspondingone of the plurality of unit areas into the outside-area attribute.9-12. (canceled)
 13. An image encoding method comprising: analyzingimage data including at least one character area and at least onepicture area, and classifying a plurality of unit areas into a characterattribute indicating that the image data is in the character area or apicture attribute indicating that the image data is in the picture area;performing scalar quantization for image data of each of the pluralityof unit areas using a corresponding one of two quantizationcoefficients, in accordance with whether the image data is classifiedinto the character attribute or the picture attribute at said analyzing;encoding the image data of each of the plurality of unit areas which isquantized at said performing scalar quantization using a correspondingone of two progressive techniques, in accordance with whether the imagedata is classified into the character attribute or the picture attributeat said analyzing; performing post quantization for the image data ofeach of the plurality of unit areas which is encoded at said encodingusing a corresponding one of two quantization parameters, in accordancewith whether the image data is classified into the character attributeor the picture attribute at said analyzing; and storing the image dataof each of the plurality of unit areas which is post quantized at saidperforming post quantization, in a predetermined storage section. 14.The image encoding method according to claim 13, wherein said performingscalar quantization includes performing scalar quantization for theimage data of each of the plurality of unit areas using a predeterminedquantization coefficient for characters, in a case where a correspondingone of the plurality of unit areas is classified into the characterattribute at said analyzing, and performing scalar quantization for theimage data of each of the plurality of unit areas using a predeterminedqualitization coefficient for pictures, in a case where thecorresponding one of the plurality of unit areas is classified into thepicture attribute at said analyzing; said encoding includes encoding theimage data of each of the plurality of unit areas using an SNRprogressive technique, in a case where the corresponding one of theplurality of unit areas is classified into the character attribute atsaid analyzing, and encoding the image data of each of the plurality ofunit areas using a resolution progressive technique, in a case where thecorresponding one of the plurality of unit areas is classified into thepicture attribute at said analyzing; and said performing postquantization section includes performing post quantization for the imagedata of each of the plurality of unit areas using a predeterminedquantization parameter for characters, in a case where the correspondingone of the plurality of unit areas is classified into the characterattribute at said analyzing, and performing post quantization for theimage data of each of the plurality of unit areas using a predeterminedquantization parameter for pictures, in a case where the correspondingone of the plurality of unit areas is classified into the pictureattribute at said analyzing.
 15. The image encoding method according toclaim 13, wherein: said analyzing includes analyzing the image dataincluding the at least one character area and at least one picture areain accordance with whether the image data represents a high-contrastimage or a low-contrast image, classifying a corresponding one of theplurality of unit areas into an high-contrast attribute indicating thatthe image data represents the high-contrast image or a low-contrastattribute indicating that the image data representing the low-contrastimage; said performing scalar quantization includes performing scalarquantization for the image data of each of the plurality or unit areasusing a predetermined quantization coefficient for characters in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the high-contrast attribute at said analyzing, and performingscalar quantization for the image data of each of the plurality of unitareas using a predetermined quantization coefficient for pictures, in acase where the corresponding one of the plurality of unit areas isclassified into the low-contrast attribute at said analyzing; saidencoding includes encoding the image data of each of the plurality ofunit areas using an SNR progressive technique, in a case where thecorresponding one of the plurality of unit areas is classified into thehigh-contrast attribute at said analyzing, and encoding the image dataof each of the plurality of unit areas using a resolution progressivetechnique, in a case where the corresponding one of the plurality ofunit areas is classified into the low-contrast attribute at saidanalyzing; and said performing post quantization includes performingpost quantization for the image data of each of the plurality of unitareas using a predetermined post quantization parameter for characters,in a case where the corresponding one of the plurality of unit areas isclassified into the high-contrast attribute at said analyzing, andperforming post quantization for the image data of each of the pluralityof unit areas using a predetermined post quantization parameter forpictures, in a case where the corresponding one of the plurality of unitareas is classified into the low-contrast attribute at said analyzing.16. The image encoding method according to claim 13, wherein: saidanalyzing includes analyzing image data including at least one titlearea and at least one body-part area, classifying a corresponding one ofthe plurality of unit areas into a body-part attribute indicating thatthe image data represents a body part of an electronic document to beencoded or a title attribute indicating that the image data represents atitle of the electronic document; said performing scalar quantizationsection includes performing scalar quantization for the image, data ofeach of the plurality of unit areas using a predetermined quantizationcoefficient characters, in a case where the corresponding one of theplurality of unit areas is classified into the body-part attribute atsaid analyzer, and performing scalar quantization for the image data ofeach of the plurality of unit areas using a predetermined quantizationcoefficient for a title, in a case where the corresponding one of theplurality of unit areas is classified into the title attribute at saidanalyzing; said encoding includes encoding the image data of each of theplurality of unit areas using an SNR progressive technique, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the body-part attribute at said analyzing, and encoding the imagedata of each of the plurality of unit areas using a resolutionprogressive technique, in a case where the corresponding one of theplurality of unit areas is classified into the title attribute at saidanalyzing; and said performing post quantization section includesperforming post quantization for the image data of each of the pluralityof unit areas using a predetermined quantization parameter forcharacters, in a case where the corresponding one of the plurality ofunit areas is classified into the body-part attribute at said analyzing,and performing post quantization for the image data of each of theplurality of unit areas using a predetermined qualitization parameterfor a title, in a case where the corresponding one of the plurality ofunit areas is classified into the title attribute at said analyzing. 17.The image encoding method according to claim 13, wherein: said analyzingincludes analyzing image data including at least an inside-area andoutside-area of a frame of an electronic document which is enclosed by aruled line, and classifying a corresponding one of the plurality of unitareas into an inside-area attribute indicating that the image data isinside the frame or an outside-area attribute indicating that the imagedata is outside the frame; said performing scalar quantization sectionincludes performing scalar quantization for the image data of each ofthe plurality of unit areas using a predetermined quantizationcoefficient for the inside-area of the frame, in a case where thecorresponding one of the plurality of unit areas is classified into theinside-area attribute at said analyzing, and performing scalarquantization for the image data of each of the plurality of unit areasusing a predetermined quantization coefficient for the outside-area ofthe frame, in a case where the corresponding one of the plurality ofunit areas is classified into the outside-area attribute at saidanalyzing; said encoding includes encoding the image data of each of theplurality of unit areas using an SNR progressive technique, in a casewhere the corresponding one of the plurality of unit areas is classifiedinto the inside-area attribute at said analyzing, and encoding the imagedata of each of the plurality of unit areas using a resolutionprogressive technique, in a case where the corresponding one of theplurality of unit areas is classified into the outside-area attribute atsaid analyzing; and said performing post quantization section includesperforming post quantization for the image data of each of the pluralityof unit areas using a predetermined quantization parameter forcharacters, in a case where the corresponding one of the plurality ofunit areas is classified into the inside-area attribute at saidanalyzing, and performing post quantization for the image data of eachof the plurality of unit areas using a predetermined quantizationparameter for the outside-area, in a case where the corresponding one ofthe plurality of unit areas is classified into the outside-areaattribute at said analyzing. 18-19. (canceled)